A laminated glass obtainable by bonding two glass plates and an interlayer film for laminated glass containing plasticized polyvinyl butyral interposed between the two glass plates is widely used in particular as a vehicular windshield.
An interlayer film for laminated glass may include only one resin layer, or may include a laminate of two or more resin layers. Including a first resin layer and a second resin layer which have different properties as two or more resin layers, an interlayer film can have various properties that are hardly achieved by a monolayer structure.
Patent Literature 1, for example, discloses an interlayer film for laminated glass having a three-layer structure including a sound insulation layer and two protective layers interposing the sound insulation layer therebetween. The interlayer film for laminated glass of Patent Literature 1 includes a sound insulation layer containing a polyvinyl acetal resin that is highly compatible with a plasticizer and a large amount of a plasticizer to exhibit excellent sound-insulating properties. The protective layers prevent bleed-out of a large amount of the plasticizer contained in the sound insulation layer to prevent lowering of adhesiveness between the interlayer film and glass.
A laminated glass including such an interlayer film for laminated glass in which two or more resin layers are laminated together, however, may cause ghost images when external light rays are seen through the laminated glass. Such ghosting often occurs especially in the case of an interlayer film for laminated glass excellent in sound-insulating properties such as that disclosed in Patent Literature 1.